System, apparatus, and method for monitoring organic compounds in a gas environment

ABSTRACT

The invention relates to a system and micro monitor apparatus, a space-, time-, and cost-efficient device to concentrate, identify, and quantify organic compounds in gas environments. The invention further relates to a method centered on gas chromatography for identifying and quantifying organic compounds in gas environments, using air as the carrier gas, without the need for a compressed pre-bottled purified carrier gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage entry of PCT/US17/27523, filed Apr.14, 2017, which claims priority to U.S. Provisional application No.62/322,980 filed on Apr. 15, 2016, both of which are incorporated hereinby reference in their entireties.

BACKGROUND OF THE INVENTION

In general, the measurements of organic compounds, including volatileorganic compounds (VOCs) in the atmosphere or other environments,require instrumentation that is large (smallest is ˜2 ft.×2 ft.×2 ft.),expensive (range $25k-500k), and requires consumable gases forchromatography, e.g., high purity helium, hydrogen, and/or nitrogencylinders. Science progress, health screening, environmental monitoring,and regulatory policy is greatly limited by these restrictions and theircosts, even more so in the developing world or disadvantagedcommunities. Current measurement tools either require the installation(and operation by a trained expert) of large gas chromatographs and/ormass spectrometers at field locations, or it requires the capture of airsamples in 1 ft. gas canisters that are then transported (evencross-oceanic distances) to be analyzed in a lab, and those measurementsare limited by what can be recovered from the canister due tocondensation and adsorption to its walls.

Occupational and industrial settings have to rely on adsorbent “tubes”or “badges” or chemically nonselective sensors that provide limiteddaily, or longer, average measurements, or data of poor accuracy andselectivity, respectively. Tools for human health screening are veryexpensive and may require tests that are either intrusive or involveradiation, so the field of human breath, or other gaseous media,analysis shows great promise for its potential as a low-cost,non-intrusive method. However, available methods for breath analysis areextremely expensive and rare given the specialized expertise needed forupkeep and operation, e.g., real-time atmospheric pressure ionizationmass spectrometers. The problem requires a robust, low-cost solutionthat can be dispersed across health care service networks.

Thus, there is a continuing need in the art for systems and methods foridentifying and quantifying organic compounds in gas environments, inparticular systems and methods which operate without the need for acompressed carrier gas. The present invention addresses this continuingneed in the art.

SUMMARY OF INVENTION

In one aspect, the invention relates to a system for analyzing a gasmixture, comprising: a filter; a trap; a chromatographic column; adetector; and a pump, wherein the trap and the pump are fluidlyconnected to form a first gas flow path, and wherein the filter, thetrap, the chromatographic column, the detector, and the pump, arefluidly connected to form a second gas flow path. In one embodiment, thedetector and the pump are fluidly connected to form a third gas flowpath. In another embodiment, the chromatographic column is a gas-solidadsorption chromatographic column. In another embodiment, thechromatographic column is a gas-liquid gas chromatography column. Inanother embodiment, the trap further comprises an adsorbent material. Inanother embodiment, the filter is an activated charcoal filter. Inanother embodiment, the detector is selected from the group consistingof a photo ionization detector, a mass spectrometer, aspectrophotometer, and a thermal conductivity detector. In anotherembodiment, the detector is a photo ionization detector. In anotherembodiment, the pump provides negative pressure. In another embodiment,the system further comprises a housing. In another embodiment, thehousing is no larger than 216 cubic inch.

In another aspect, the invention relates to a method of analyzing atleast one chemical compound in a gas mix, the method comprising:directing flow of the gas mix through a trap to concentrate at least aquantity of the at least one chemical compound; redirecting flow of thegas mix through a filter to provide a filtered gas flow to the trap;releasing at least a quantity of the at least one concentrated chemicalcompound into the filtered gas flow; and analyzing at least a quantityof the released at least one concentrated chemical compound. In oneembodiment, the at least one chemical compound comprises at least oneorganic compound. In another embodiment, the at least one organiccompound comprises at least one volatile organic compound. In oneembodiment, analysis of at least a quantity of the released at least oneconcentrated chemical compound comprises running at least a quantity ofthe released at least one concentrated chemical compound through a gaschromatography column. In one embodiment, the gas chromatography columnis a gas-solid adsorption chromatographic column. In another embodiment,the chromatographic column is a gas-liquid gas chromatography column. Inanother embodiment, analysis of at least a quantity of the released atleast one concentrated chemical compound comprises identifying the atleast one organic compound by a method selected from the groupconsisting of photo ionization, mass spectrometry, spectrophotometry,and thermal conductivity. In another embodiment, analysis of at least aquantity of the released at least one concentrated chemical compoundfurther comprises quantifying the at least one chemical compound. In oneembodiment, the gas mix is an environmental gas mix. In anotherembodiment, the gas mix comprises gases exhaled or otherwise emitted bya living subject. In another embodiment, the gas mix is air.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of preferred embodiments of theinvention will be better understood when read in conjunction with theappended drawings. For the purpose of illustrating the invention, thereare shown in the drawings embodiments which are presently preferred. Itshould be understood, however, that the invention is not limited to theprecise arrangements and instrumentalities of the embodiments shown inthe drawings.

FIG. 1, comprising FIGS. 1A through 1H, is a schematic flow diagram of asystem or an apparatus according to two embodiments of the invention, asthey relate to the flow of gases, i.e., air, with or without analytes,through the system or apparatus.

FIG. 2, comprising FIGS. 2A and 2B, is a partial schematic electriccircuit of an apparatus according to one embodiment of the invention.

FIG. 3 is a simplified electrical diagram showing the control systemaccording to one embodiment of the present invention.

FIG. 4 is a perspective view of an apparatus according to one embodimentof the invention.

FIG. 5, comprising FIGS. 5A through 5D, depicts views of a spool aroundwhich a gas chromatography column is wound and a cover for same.

FIG. 6, comprising FIGS. 6A through 6E, depicts views of an oven andrelated components for a gas chromatography column.

FIG. 7, comprising FIGS. 7A and 7B, depicts two views of a block thatsurrounds the exterior of the adsorbent trap for heating and cooling.

FIG. 8, comprising FIGS. 8A and 8B, depicts two views of a component ofa housing that contains the photo ionization detector, the componentcomprising an inlet port.

FIG. 9, comprising FIGS. 9A and 9B, depicts two views of a component ofa housing that contains the photo ionization detector, the componentcomprising an outlet port.

FIG. 10, comprising FIGS. 10A and 10B, depicts two views of a componentof a housing that contains the photo ionization detector, the componentcomprising three holes for the detector pins, i.e., for power andsignal.

FIG. 11A is a chart depicting the results of an experiment for cooledsample collection and desorption of a high volatility analyte using theapparatus according to one embodiment of the invention.

FIG. 11B is a chart depicting the results of an experiment forseparating a two component mixture with air as carrier gas using anapparatus according to one embodiment of the invention.

FIG. 12A is a chart depicting the results of an experiment testing the“trap-and-run” mode of one embodiment of the invention.

FIG. 12B is a chart depicting the results of an experimentalchromatogram of an ambient air sample.

FIG. 13 is a flow chart of a real-time analysis method for identifyingand quantifying organic compounds in gas environments according to oneembodiment of the invention.

FIG. 14 is a flow chart of a gas chromatography method for identifyingand quantifying organic compounds in gas environments according to oneembodiment of the invention.

FIG. 15 is a flow chart of a gas chromatography method for identifyingand quantifying organic compounds in gas environments according to oneembodiment of the invention.

DETAILED DESCRIPTION

The invention relates to a system for concentrating, identifying, andquantifying organic compounds in gas environments. The invention relatesin particular to a micro monitor apparatus, a space-, time-, andcost-efficient device to concentrate, identify, and quantify organiccompounds in gas environments. The invention further relates to a methodcentered on gas chromatography for identifying and quantifying organiccompounds in gas environments, without the need for a compressedpre-bottled purified carrier gas.

The invention provides an unexpected advancement in analyticalchemistry, as the method, the system and apparatus of the invention aredesigned to work without compressed gas, thus creating significantimprovements over existing systems. Existing systems known in the artare big, cumbersome and expensive. On the other hand, an apparatus ofthe invention can be, in one embodiment, small, approx. 6″×6″×6″, andlow-cost, e.g., <$1000. In another embodiment, the system or apparatusof the invention is a monitor for organic compounds in the atmosphere orother gas environments, which are typically present at traceconcentrations, e.g. parts per billion or parts per trillion. Itprovides simultaneous real-time measurements of total concentrations,and chemical resolution via periodic, gas chromatography without the useof compressed gas cylinders. The monitor provides unprecedented small,portable, and low-cost capabilities to identify and measure theprominent organic compounds.

The system or apparatus of the invention may be used for research orenvironmental monitoring at outdoor monitoring sites; indoors inindustrial settings or in residences; as a low-cost health screeningdevice through analysis of breath, other bodily substances or surfaces;or for other applications where organic compound measurements arecritical (e.g. quality control for food, beverage, or chemicalproduction; military monitoring, low-cost laboratory data collection;and monitoring volatile organics in water). A specific application isfor use as a detector of Volatile Organic Compounds (VOCs) in air,compounds that are toxic and/or carcinogenic (e.g. benzene), andreactive precursors to ozone and secondary organic aerosol, which arethe two types of air pollutants with the largest health effects.

The invention provides a functional, space-, time-, and cost-efficientapparatus and methods to concentrate, identify, and quantify organiccompounds in gas environments, by, among other means, effectivelyreplicating the capabilities of a gas chromatograph with the addedfeature of real-time measurements for high frequency data. The inventionrelies in part on a number of key advancements: (1) the ability to dogas chromatography of prominent organic compounds in gas streams usingair, i.e., nitrogen (N₂), oxygen (O₂), and argon, with trace carbondioxide (CO₂), water, and methane, drawn through a hydrophobic layer anda filter, as the carrier gas, and a small pump, rather than requiringhigh purity gas cylinders, i.e., large, costly high purity helium,hydrogen, and/or nitrogen from high pressure cylinders; (2) the smallsize and cost requires specially engineered parts and electronics, andthus creates the ability to use the device to take portable measurementsor measurements at hard to access locations, including as part ofnetworks made up of multiple devices; (3) simultaneous real-timemeasurements with 1 Hz frequency coupled with capabilities to identifythe specific compounds with chromatography, something that could only bedone before by a select few instruments larger in costs, size, andmaintenance, e.g., Ionicon customized proton transfer reaction massspectrometers. This results in research-grade high quality data on anextensive suite of organic compounds, especially those with 1 to 25carbon atoms.

Definitions

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention, while eliminating,for the purpose of clarity, other elements found in the art related togas chromatography, gas stream purification, adsorption/desorptionand/or trapping of organic compounds, detection of organic compounds,gas pumping, calibration of chromatographic systems, and the like. Thoseof ordinary skill in the art may recognize that other elements and/orsteps are desirable and/or required in implementing the presentinvention. The disclosure herein is directed to all such variations andmodifications to such elements and methods known to those skilled in theart.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods, materialsand components similar or equivalent to those described herein can beused in the practice or testing of the present invention, the preferredmethods and materials are described.

As used herein, each of the following terms has the meaning associatedwith it in this section.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

“About” as used herein when referring to a measurable value such as anamount, a temporal duration, and the like, is meant to encompassvariations of ±20%, ±10%, ±5%, ±1%, or ±0.1% from the specified value,as such variations are appropriate.

Throughout this disclosure, various aspects of the invention can bepresented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, 6 and any wholeand partial increments therebetween. This applies regardless of thebreadth of the range.

Detailed Description

Referring now in detail to the drawings, in which like referencenumerals indicate like parts or elements throughout the several views,in various embodiments, presented herein are the system or apparatus,and methods for identifying and quantifying organic compounds in gasenvironments.

In one aspect, the invention relates to a system or apparatus comprisingvarious components and devices capable of managing and analyzing gasflows. For example, as shown in FIG. 1A, an exemplary system 100 mayinclude sampling inlets 110 and 120, adsorbent bed trap 130, filter 135,heater 140, pump 150, detector 151, chromatographic column 152,chromatographic column heater 153, calibration source 154, and conduits155, 156 and 157 fluidly connecting these components as necessary.Sampling inlets 110 and 120 can be any type of standard port, with orwithout the capability of being shut off. The inlets can includehydrophobic membranes that reduce water entry. The adsorbent bed trap130 can be made of any suitable material capable of reversibly adsorbinga chemical compound, in particular an organic compound, and morespecifically a volatile organic compound. In some embodiments, theadsorbent trap may comprise silica gels and/or beads in a multi-layerconfiguration. Filter 135 can be made of any suitable type of filtrationmaterial capable of retaining a chemical compound, in particular anorganic compound, and more specifically a volatile organic compound. Inone embodiment, filter 135 is made of activated charcoal. Heater 140 canbe any suitable heater, for example a cartridge heater, capable ofheating adsorbent bed 130 and facilitate desorbtion of a chemicalcompound from adsorbent bed 130. Pump 150 can be any suitable pumpcapable of generating pressure for operating system 100. In oneembodiment, pump 150 generates negative pressure. In another embodimentor flow scheme, the positive pressure exhaust of pump 150 can be usedfor desorption and/or gas chromatography via a valve upstream of some orall system elements. Detector 151 can be any suitable detector forsensing a chemical compound, in particular an organic compound, and morespecifically a volatile organic compound. Chromatographic column 152 canbe any suitable adsorbing surface, for example a gas chromatographiccolumn. In some embodiments, the Chromatographic column comprises 100%Dimethylpolysiloxane (e.g. DB-1) or trifluoropropylmethyl polysiloxane(e.g. DB-200, DB-210) for the active phase. In other embodiments, theChromatographic column is a porous polymer column, for example aPoraplot-Q column. The adsorptive materials used in the trap andChromatographic column allow for efficient collection of analytes overlong periods followed by thermal desorption and chromatographicseparation of the materials in air. The system is advantageous becauseit protects the analytes and adsorbent materials from thermaldegradation with oxygen. In this way, the system provides the ability toquantify individual analytes with higher precision than comparableequipment.

In some embodiments, the device may use traditional silica columns. Inother embodiments, the device comprises passivated steel columns, forexample RTX-1. Passivated steel columns provide faster and more accurateheating and cooling due to higher thermal conductivity, as well as moresecure connections with traditional ferrules and fittings. As a result,the use of passivated steel columns increases reliability and reducesthe amount of maintenance necessary in the field.

Chromatographic column heater 153 can be any suitable heater, forexample a cartridge heater, capable of heating chromatographic column152, in particular capable of generating a programmed temperature ramp.In some embodiments, the system of the present invention includesmultiple heated zones. For example, the entire system including alltransfer lines may be heated, in order to optimize transfer efficiency.In some embodiments, the column 152 and heater could be integrated intoa “GC-on-a-chip”, “column-on-a-chip” or “gas chromatograph-on-a-chip”arrangement, whereby the “column” is connecting grooves that are milledor etched into a plate made of any appropriate material known in theart, including but not limited to metal, silica, or glass. The etched ormilled material may then be treated with an active column phase so thatit behaves like a traditional column.

Calibration source 154 is any suitable calibration source for theappropriate detector and/or chromatographic column in use. In oneembodiment, the calibration source comprises a single volatile organiccompound. Conduits 155, 156 and 157 may be tubing made from materialssuch as, but not limited to, polyether ether ketone (PEEK), stainlesssteel, polytetrafluoroethylene (PTFE), or any other suitable material aswould be understood by those skilled in the art.

In some embodiments, chromatography column 152 may utilize gas-liquidadsorption chromatography. In some embodiments, chromatography column152 may comprise different active column “phases”, i.e. adsorptivechemicals that are less prone to thermal degradation at hightemperatures.

In one aspect, chromatography column 152 may utilize gas-solidadsorption chromatography which is less prone to degradation at hightemperatures in the presence of oxygen in air. Another advantage ofusing a gas-solid adsorption chromatographic column is that it is lessaffected by water vapor or carbon dioxide. The gas-solid separationoccurs across the trapping/concentrating adsorbent bed and the opentubular column that can be adapted with a variety of specific columnswith different adsorbents, e.g., divinylbenzene, or molecular sieve. Inone embodiment, the chromatography column is a column capable of usingthe major components of air as carrier gas, i.e., nitrogen and oxygen.Since nitrogen is the dominant component of air and similar in structureto oxygen, their performance as a carrier gas are similar.

In one embodiment, the system or apparatus are operated using vacuum gaschromatography, e.g., by providing a source of negative pressure. Inanother embodiment, the system or apparatus is operated using positivepressure gas chromatography. The differences between various embodimentsdepend on the orientation of the pump, valves, and connections, whereina variety of configurations can be envisioned by one skilled in the art.In one embodiment, the system or apparatus employs elements of fastchromatography, e.g., a microbore column. In one embodiment, themicrobore has a 0.05 to 0.15 mm inner diameter. In another embodiment,the column has a 0.15 to 1.00 mm inner diameter. In one embodiment, themicrobore has a 0.53 mm inner diameter. In one embodiment, thechromatography column has a 0.05 to 1.00 mm inner diameter. In anotherembodiment, the chromatography column has a 0.53 mm inner diameter. Inanother embodiment, the system or apparatus employs other columnsdepending on target analytes and pump specifications. In otherembodiments the system or apparatus uses a gas-liquid chromatographycolumn that has a stationary phase resistant to oxygen degradation atthe operating temperatures.

The system of the present invention may also include a coupledcollection trap and chromatography control and analysis module, capableof adjusting flows (rate and direction) and temperatures in a way thatis customizable to any particular set of analytes, but optimized for abroad range of analytes. In one example, the control and analysis modulecollects analytes in a cooled state at temperatures ≤5° C. for up to15-30 minutes. In another example, the control and analysis modulereverses the flow of air through the trap and supplies the trap withclean air through a charcoal filter. In another example, the moduleheats the trap rapidly to desorb analytes onto the column, cooled to<5-10° C. depending on the analytes. This or other examples may furthercomprise a cryotrap or cryofocusing element at the start of the column.Use of a cooling element in the trap and column presents an advantageover systems known in the art, because cooling the trap and the columnallows for improved analyte retention, focusing, and performance. In yetanother example, the module may begin operation with a set temperaturehold, followed by heating the system at a pre-determined ramp rate,while adjusting the various flows to attain maximum separationefficiency of the column. In this or other examples, the system mayfurther comprise a pressure constriction at the head of the column tooptimize flow with a pump.

In another example, the system may begin collecting a second samplewhile still analyzing a first sample. The control and analysis modulemay accomplish this by opening a valve to a bypass line around the trapin gas-chromatography-only mode. This allows the rest of the gaschromatography analysis run to operate at a flow rate optimized for thelatter portion of the run. In another example, the module executes aheating program and GC analysis, followed by a rapid cooling stage toprepare the system for the next analysis run.

As shown in FIG. 1A, system 100 comprises a detector 151. In oneembodiment, detector 151 is a sensing element, such as a photoionizationdetector (PID), a miniature mass spectrometer, a spectrophotometer, athermal conductivity detector, any other suitable spectrometer, or anyother suitable detector. In one aspect, the invention relates to asystem or apparatus employing photo ionization detection. Changing theionization potential of the PID lamp, e.g., between 9.6-11.7 eV viachanging the halogen gas inside the lamp, affords the apparatus biggerselectivity across a range of analytes with different ionizationenergies, i.e., from about 7 eV to about 11.7 eV. In one embodiment, theuse of a 9.6 eV lamp allows selective ionization of aromatichydrocarbons, also known as BTEX, and other compounds with ionizationenergies below 9.6 eV. Benzene, toluene, ethylbenzene, m&p-xylene,o-xylene, and 3-trimethylbenzene isomers are examples of compounds withionization energies lower than 9.6 eV. In other examples, the ionizationpotential of the PID lamp is 10.0 eV, or 10.6 eV. In another embodiment,the use of a miniature mass spectrometer as a detector extends thetunable selectivity of the device.

In one aspect, the invention relates to a system or an apparatus whichis automated by a microprocessor and software that operates the systemof valves, heaters, coolers, and collects data on the PID signal,relative humidity, pressure, and temperature across the system. In someembodiments, the collected relative humidity, pressure, and temperaturedata is used to correct data from the PID. In one embodiment, the systemcomponents such as those in the system of FIG. 1A may be electricallyconnected according to the schematic electric circuits 210 and 220depicted in FIGS. 2A and 2B, respectively. In one embodiment, thecomponents are selected from the group consisting of cartridge powersupplies 211 and 221, heater 212, PID 213, analog to digital converterand gain amplifier 214, microcontroller 215, level shifter 216,thermocouple 217, relay 218, pump 222, digital to analog converter 223,and operational amplifier 224. In some embodiments, the controlcircuitry comprises at least one microcontroller, wherein some or allmicrocontrollers comprise multiple processing cores. In someembodiments, the microcontroller 215 comprises a single board computer(SBC), such as an Arduino®. In other embodiments, the microcontrollercomprises a Programmable System on a Chip (PSoC), such as onemanufactured by Cypress®. In other embodiments, the microcontrollercomprises a Field-Programmable Gate Array (FPGA). In some embodiments,the control circuitry comprises ultra-low-noise circuits. In someembodiments, the control circuitry includes a wireless communicationlink, comprising wi-fi, cellular connectivity, BlueTooth® or any otherwireless communication system known in the art. The wirelesscommunication link allows for some or all of the functions of the systemto be executed remotely, and some or all of the data collected to betransferred to a remote system for analysis. In some embodiments, thedevice may operate automatically without any user intervention, locallyor remotely.

Referring now to FIG. 3, a simplified control system diagram 250 of oneembodiment of the present invention is shown. Microprocessor 251executes a series of instructions which coordinates the collection ofdata from the various sensors and actuation of the various electricaland mechanical elements of the system. Microprocessor 251 is connectedto pump controller 252, which in turn controls pump 150. Microprocessor251 is further connected to a set of relays 253, PID data collector 256,environmental sensors 258, and Peltier Plate controller 259. Relays 253are electrically connected to electronic valve actuators 254, which inturn mechanically control the various valves in the system in order tocreate the flow paths described in FIGS. 1C-1G, including but notlimited to valves 102, 172, and 177. PID data collector 256 receivessignals from PID 151 and converts that data into a form recordable bymicroprocessor 251. PID data collector 256 may also contain controlcircuitry for microprocessor 251 to send instructions to PID 151.Environmental sensors 258, periodically or on demand, sendsenvironmental data to microprocessor 251 in order to facilitate controlof the system. The environmental sensors may be any sensors from the setof temperature sensors, humidity sensors, pressure sensors, or any othersensors known in the art. Peltier plate controller 259 is electricallyconnected to Peltier plates 141 and 183, and through it themicroprocessor 251 can independently regulate or disable the coolingfunction of plates 141 and 183. Microprocessor 251 is shown as a singleelement, but it is understood that the functions of microprocessor 251may be split across multiple microprocessors in order to achieve higherefficiency. In one embodiment, control system diagram 250 includes asecond microprocessor that controls the temperature-control elements ofthe system of the present invention, including the ovens and the Peltierplates.

In some embodiments, Microprocessor 251 is electrically connected tosome combination of display 255 and wireless communication module 257.Display 255 displays system status and error messages in order tofacilitate operation and troubleshooting of the system. In someembodiments, display 255 is an LCD display. Wireless communicationmodule 257 facilitates communication between microprocessor 251 and aremote device. In some embodiments, the remote device periodicallyreceives measurement information or system status data from themicroprocessor 251. In some embodiments, the wireless communicationdevice also receives control signals or commands from a remote device,allowing a remote user to exercise control over the functionality of thesystem.

With reference again to the exemplary system 100 of FIG. 1A, a gasstream, e.g., air, is pulled in through two sampling inlets, i.e.,tubes, 110 and 120. In one embodiment, the gas is pulled by negativepressure via a pump 150 located at the far downstream end of theinstrument. The real time inlet 120 is connected to a tube which leadsdirectly to detector 151, i.e., PID, following an on/off valve 101. Thisstream of gas through the tube connected to inlet 120 provides real-timemeasurements of total organic compounds in the gas stream, or the totalconcentration of organic compound sensitive to the detection method.

Inlet 110 concentrates the trace concentrations of organic gases onto anactive, or inert, adsorbent surface or packed bed 130 that isthermoelectrically cooled in an aluminum block. In one embodiment, theadsorbent bed functions as a trap for the organic gases. After anadjustable time interval of concentrating trace organics, a valve 102switches to draw air in through a charcoal filter 135 that provides airfree of organic compounds. In one embodiment, the time interval isbetween 2 and 30 minutes. The on/off valve 101 on the “real-time” inletis activated so that all flow is directed through the charcoal filterproviding clean air which acts as the carrier gas for a chromatographiccolumn 152. The flow of clean air from inlet 110 is directed through thecharcoal filter 135, the adsorbent bed 130, and then into a gaschromatography column 152. The adsorbent bed/surface 130 is slowlyheated, for example by heater 140, to thermally desorb, or release, theorganic compounds as a function of their vapor pressure or polarity,effectively providing a rough separation method. The effluents from thistrap proceed into a capillary gas chromatography column 152 thatoperates on the principle of gas-solid adsorption chromatography, orgas-liquid chromatography. In one embodiment, the gas chromatographycolumn is replaced by a gas chromatography microfluidic chip. The columnis wrapped around a custom-machined aluminum cylinder, or themicrofluidic chip is placed against an aluminum block, that is heated byheating cartridges 153 at a rate that further separates/resolves theanalytes in the column. In one embodiment, the column is positionedwithin a custom-machined aluminum oven. In one embodiment, the aluminumcylinder is as described in FIGS. 5A and 5B machined in the shape of aspool. In another embodiment, the cylinder comprises various machinedindentations, cavities or channels which can be used for, but notlimited to, fixation of the cylinder to the rest of the apparatus, forappending heating/cooling elements, or for venting. In anotherembodiment, the cylinder further comprises two grooves in the edge ofthe spool for entrance/exit of the chromatographic column. In anotherembodiment, the cylinder is covered by a cylindrical cover as describedin FIGS. 5C and 5D.

Another embodiment of the oven is shown in 331 in FIGS. 6A-6E. In thisembodiment, the oven is an aluminum housing as shown in FIG. 6A,depicting a top view, and 6B, depicting a front view. The oven maycomprise machined aluminum, and comprises mounting holes 333 and a setof evenly spaced holes 332 in a circular pattern. The chromatographictubing enters the oven 331 through inlet/outlet holes 334 or 335, thenwraps around the holes 332 before exiting the oven through the other ofinlet/outlet holes 334 or 335. The oven is enclosed with oven cover 336shown in FIG. 6C, comprising mounting holes 337 that correspond tomounting holes 333. In some embodiments, the oven further comprisesPeltier plate 183 shown in FIG. 6D, showing a front view, and 6E,showing a side view. Peltier plate 183 comprises plate 342 whichgenerates a temperature differential between cold side 345 and hot side346 in response to electric current provided through wires 343 and 344.Plate 342 operates based on the thermoelectric effect, also known in theart as the Peltier effect. In some embodiments, a heat sink comprisingone or more fins may be affixed to the hot side 346 of Peltier plate 183to increase the effectiveness of heat transfer from cold side 345 to hotside 346.

The effluent from the chromatographic column 152 enters the PID 151, orother detector, where the mass of each compound is quantified based onthe PID signal, and an atmospheric concentration can be calculated viathe known concentrating flow rate during sampling. Similar to normalchromatography, the identity of each compound can be reliably determinedbased on the time it elutes from the column-adsorbent bed system that isheated with the same heating program each run. Following completion,valve 101 opens and the system reverts to real-time measurements and thechromatography inlet cools via fans and thermoelectric coolers.Following the PID, both flows exit via pump 150. A built-in calibrationmethod is controlled by an on/off valve 103. In one embodiment, thesystem effuses a constant amount of evaporating calibrant, e.g., asingle VOC, through a critical orifice into one of the sample inlets,which is periodically used to calibrate the system. In one embodiment,the calibrant in vessel 154 is introduced through the real time inlet.Consistent, known, or calibrated relative response factors for the PIDallow for cross-calibration to all the other measured compounds.

Another embodiment of the invention is described in system 160 of FIGS.1B-1H. System 160 of FIG. 1B shows the overall structure of the variousparts and how they are connected. FIGS. 1C-1G depict flow diagrams ofthe various modes of system 160. Particularly, FIG. 1C depicts the Trapmode, FIG. 1D depicts the Desorb/Run mode, FIG. 1E depicts the Real-Timemode, FIG. 1F depicts the Calibration mode, and FIG. 1G depicts theTrap-and-Run mode. The operation of system 160 is similar to theoperation of system 100, but with the added step of reversing the flowof air through the adsorbent trap 130 in between the trapping step andthe desorbing step. FIG. 1H shows the materials used in one embodimentof the invention.

Referring to FIG. 1C, the flow diagram 161 of the Trap mode of system160 is shown. A vacuum is created by the pump 150 and unfiltered airenters through the inlet 110. Air proceeds first through a hydrophobicPM filter 171 before being routed by valve 172 through the near end ofthe adsorbent trap 130, where some compounds are trapped via adsorptionfor later analysis. In some embodiments, the trap may be cooled usingpeltier plate 141. Cooling the trap 130 allows for improved analyteretention, focusing, and performance. The remaining air proceeds throughvalve 177 and out of the system through the pump 150.

Referring now to FIG. 1D, a flow diagram 162 of the Desorb/Run mode ofsystem 160 is shown. Once the trapping step is complete, the adsorbenttrap 130 contains some compounds to be analyzed. Valves 172 and 177change the flow direction as shown in flow diagram 162, drivingunfiltered air through the inlet 110 followed by hydrophobic PM filter171, then routing the unfiltered air through activated carbon filter 135to remove most compounds and send filtered air through the system. Thefiltered air proceeds through flow constrictor 176 before entering theadsorbent trap 130 through the far end, a flow direction opposed to theflow of diagram 161. In some embodiments, a heater or heaters 140 areengaged during the Desorb/Run mode 162, speeding the rate at whichcompounds desorb from the adsorbent trap 130. The desorbed compounds,entrained in the filtered air, proceed through valve 172 to capillarygas chromatography column 182, which also may optionally be heated.Column 182 operates similarly to column 152 of FIG. 1A. The effluentfrom column 182 enters PID or other detector 151, where the mass of eachcompound is quantified. Finally, air proceeds through valve 184 and pump150 before exiting the system. In some embodiments, the system furthercomprises Peltier plate 183, which is affixed to oven 182 and providesthermoelectric cooling in some phases of system air flow.

The flow constrictor 176 functions to restrict flow prior to enteringthe adsorptive trap and the column, ensuring that pressure is low acrossthe whole column and increasing resolving potential (i.e. the number of“plates” in the column). This presents significant advantages oversimilar systems known in the art.

FIG. 1E depicts a flow diagram 163 of the Real-Time mode of system 160.In real-time mode, flow is similar to real-time mode of the system 100of the present invention. Unfiltered air enters through a secondaryinlet 120 and then through hydrophobic PM filter 187, before proceedingthrough valve 101 directly to PID or other detector 151. The air thenflows through valve 184 and out of the system via pump 150. Oneadvantage of the system of the present invention is the ability tocontinuously monitor in real-time mode, while periodically switching toa fuller GC analysis described in FIGS. 1C, 1D, and 1F. In someembodiments, a high reading or spike in total concentrations detectedduring real-time sampling triggers a switch to trap-and-run mode,thereby allowing for more precise measurement of the chemicalcomposition of the detected compounds. In some embodiments, thetrap-and-run measurements may be used to discern the source of one ormore chemical compounds.

A further operating mode is contemplated by combining the flow paths ofFIGS. 1C and 1E. In embodiments of the device that support the real-timeflow path 163, the system of the present invention may collect compoundscontinuously via flow path 163 while simultaneously collecting compoundsin the trap via trap flow path 161. In such a “real-time and trap” mode,the system may collect high time-resolution data of total concentrations(real-time data) then at the end of the collection period, the compoundsfrom the trap may be analyzed to determine the chemical speciation ofthe mixture over the period during which high time resolution data wascollected. This mode is of particular use to capture events that happenover short periods where the duration and features of the event are ofinterest and where it is also advantageous to know the chemicalspeciation of the mixture over that period.

FIG. 1F depicts a flow diagram 164 of Calibration mode of system 160.Operation of calibration mode is similar to that of real-time mode 163,except that instead of running unfiltered air through the system fromthe inlet of filter 187, valve 101 closes and valve 103 opens to pull ina constant amount of a standard evaporating calibrant 154. Similarly tothe calibration flow of system 100, calibration mode 164 compares theresults of from detector 151 with known relative response factors,allowing for cross-calibration to other measured compounds.

FIG. 1G depicts a flow diagram 165 of the Trap-and-Run mode of system160. In this mode, two parallel flow pathways are opened at once. In thefirst path, unfiltered air enters inlet 110 and proceeds through filter171 to charcoal filter 135. The filtered air runs through valve 178 andflow constrictor 179 before passing through the column 182, in whichorganic particles from a previous run are already present. In someembodiments, the flow constrictor 179 may be of a different size, suchthat the flow rate of the filtered air through the column may beadjusted or optimized to be more effective for separating and detectingcompounds. The organic particles are freed and pass, entrained infiltered air, into PID or other detector 151 before being pumped out ofthe system by pump 150. Simultaneous to the first flow, a second flowpath pulls unfiltered air through filter 171 then through valve 172 intotrap 130, where some particles become trapped for a future run.

By alternating between this mode and the desorb/run mode depicted inFIG. 1D, the system of the present invention can run more efficientlyand spend more time sampling.

FIG. 1H depicts the various materials used in the flow conduits incertain embodiments of the invention. Segments labeled with a “P”comprise polyether ether ketone (PEEK). Segments labeled with an “S”comprise stainless steel. Segments labeled with a “T” comprise Tygon orTeflon. The materials described herein are not meant to be limiting, butmerely depict an example of the materials that could be used in certainconfigurations of the system of the present invention.

In another aspect, the system components may be housed in a single ormulti-compartment apparatus 300 as described in FIG. 4. In oneembodiment, the size of the apparatus is about 6″×6″×6″, or no more than216 cubic inch in volume. In one embodiment, the apparatus includesvarious parts, e.g., a housing 310, a column oven and spool 320, a powersupply 330, a microcontroller and custom circuit board(s) 340, adetector housing 350, a pump 360, a calibration unit and activatedcarbon filter 370, a trap heating and cooling block 380, and trapcooling fins 390. In one embodiment, the gas chromatography unit 320further comprises cylindrical parts 321 and 322. As described elsewhereherein, cylinder 321 can be machined as a spool on which achromatographic column can be wound. In one embodiment, the apparatus ofthe invention further comprises block 381 as shown in FIGS. 7A and 7B,that surrounds the exterior of the adsorbent trap for heating andcooling. In another embodiment, the apparatus of the invention comprisesblock 382 as shown in FIGS. 7C (depicting a front view) and 7D(depicting a top view). The block heater or heaters may be positioned inchannels 385. In some embodiments, block 382 comprises two halvesseparated at a center seam 386. In some embodiments, thermal couple ispositioned in hole 384 to monitor the temperature of the block.

In one embodiment, the apparatus of the invention further comprises acomponent 351 of housing 350 that contains the photo ionizationdetector, component 351 comprising an inlet port. In another embodiment,the apparatus of the invention further comprises a component 352 ofhousing 350 that contains the photo ionization detector, component 352comprising an outlet port. In an alternate embodiment shown in FIG. 9C,the apparatus of the invention further comprises a component 362 ofhousing 350 that contains the photo ionization detector, component 362comprising multiple outlet ports 367 and mounting holes 366.

In another embodiment, the apparatus of the invention further comprisescomponent 353 of housing 350 that contains the photo ionizationdetector, component 353 comprising three holes for the detector pins,i.e., for power and signal. In one embodiment, the parts are connectedaccording to schematic 100. In another embodiment, the parts areconnected according to schematics 210 and 220.

One additional advantage of the small size of the system of the presentinvention is that the column oven 331 has a lower mass than wouldtypically be needed, and thus also a lower thermal mass. Ovens withlower thermal mass are capable of tighter temperature regulation becausethey are capable of storing (and re-radiating) less heat than largerovens, allowing them to cool faster when power is removed.

In other aspects, the invention relates to methods for identifying andquantifying organic compounds in gas environments. Referring to FIG. 13,an exemplary method of a real-time analysis 400 is shown. In oneembodiment, the real-time analysis method 400 comprises step 410 ofapplying either positive or negative pressure, e.g., applying suctionwith a pump, which will force a gas mix through a system or apparatus,e.g., a system or apparatus of the invention. Real-time analysis method400 further comprises step 420 of sampling a gas mixture, e.g., air,through a sampling inlet, e.g. sampling inlet 120 as shown in FIG. 1A aspart of system 100. Real-time analysis method 400 further comprises step430 of detecting organic compounds in a gas mixture. Detection can beaccomplished by a PID detector such as for example detector 151 as shownin FIG. 1A as part of system 100.

In another aspect, the invention relates to a method for identifying andquantifying organic compounds in gas environments, the method comprisinga chromatography step. In one embodiment, the chromatography step isperformed without the need for a compressed pre-bottled purified carriergas, but rather by using purified air as a carrier gas. As shown in FIG.14, in one embodiment the method is gas chromatography analysis method500. Gas chromatography analysis method 500 comprises step 510 ofapplying either positive or negative pressure, e.g., applying suctionwith a pump, which will force a gas mix through a system or apparatus,e.g., a system or apparatus of the invention. Method 500 furthercomprises step 520 of sampling a gas mixture, e.g., environmental air,through a sampling inlet, e.g. sampling inlet 110 as shown in FIG. 1A aspart of system 100. Gas chromatography analysis method 500 furthercomprises step 530 of directing flow of the gas mix through a trap toconcentrate at least a quantity of a chemical compound, wherein theorganic compound is trapped on a bed of adsorbent material 130 such asshown for example in FIG. 1A as part of system 100. Method 500 furthercomprises step 540 of redirecting flow of the gas mix through a filterto provide a filtered gas flow to the trap, thus providing gas mix,e.g., air, free of organic compounds. Step 540 of method 500 can beaccomplished for example by diverting the flow of sampled gas through anactivated carbon filter 135, for example as shown in FIG. 1A as part ofsystem 100. Filtration removes all or part of the organic compounds inorder to provide clean carrier gas, e.g., clean air. Gas chromatographyanalysis method 500 further comprises step 550 of releasing at least aquantity of concentrated chemical compounds into the filtered gas flow,for example by sequential thermal desorption of organic compounds,wherein the previously trapped organic compounds are desorbed from thebed of adsorbent material 130 by slowly increasing temperature, forexample by using a heater 140 as shown in FIG. 1A as part of system 100.Gas chromatography analysis method 500 further comprises step 560 ofseparating at least a quantity of the released concentrated chemicalcompounds. In one embodiment, the separation comprises separatingorganic compounds, e.g., by gas chromatography. Organic compoundsdesorbed from the bed of adsorbent material are entrained by clean airprovided by filtration into a chromatographic column, for example column152 as shown in FIG. 1A as part of system 100. Gas chromatographyanalysis method 500 further comprises step 570 of detecting organiccompounds in the chromatographic column gas effluent. Detection can beaccomplished by a PID detector such as for example detector 151 as shownin FIG. 1A as part of system 100, which can be for example a photoionization detector (PID).

Referring to FIG. 15, an alternate embodiment 600 of the method of theinvention is shown. Method 600 is similar to method 500, but includesthe step 535 of reversing the direction of flow through the trap afterdirecting the flow of gas through a trap, but before redirecting theflow through a filter to provide filtered gas flow to the trap.

EXPERIMENTAL EXAMPLES

The invention is further described in detail by reference to thefollowing experimental examples. These examples are provided forpurposes of illustration only, and are not intended to be limitingunless otherwise specified. Thus, the invention should in no way beconstrued as being limited to the following examples, but rather, shouldbe construed to encompass any and all variations which become evident asa result of the teaching provided herein.

Without further description, it is believed that one of ordinary skillin the art can, using the preceding description and the followingillustrative examples, make and utilize the compositions of the presentinvention and practice the claimed methods. The following workingexamples therefore, specifically point out the preferred embodiments ofthe present invention, and are not to be construed as limiting in anyway the remainder of the disclosure.

Example 1

As depicted in FIG. 11A a system of the invention was used to detectacetone in an air/acetone mixture. First, a sample inlet was exposed toa pulse of acetone in air. The system was allowed about ten minutes totrap and concentrate acetone in a cooled bed of adsorbent material.After about ten minutes, the adsorbent bed heaters were powered toprovide a temperature gradient increase of about 60° C./minute. Afterabout 30 seconds a peak was detected in the output of the photoionization detector.

Example 2

As depicted in FIG. 11B a system of the invention was used to separateand detect iso-pentane and acetone using air as carrier gas in a gaschromatography method. Six separate runs of the separation method,including three runs performed after twenty hours of continuous running,demonstrated the high efficacy of separation and repeatability overtime.

Example 3

As depicted in FIG. 12A, a system of the invention was used in trap modeand run mode for the complete autonomous device without any externalpressure or vacuum and no additional equipment. The figure shows a“chromatogram” with the PID sensor output, trap temperature, and oventemperatures along the Y axis and run-time along the X axis. Ananalytical standard mixture of single-ring aromatic compounds wassampled from the gas phase, trapped, retained, and then injected ontothe column where it was separated under vacuum over the automatictemperature program, and then measured on the PID. The compounds showninclude the common and challenging BTEX compounds that are of highinterest in the scientific, regulatory, and commercial community.Specific analytes measured and labeled are benzene, toluene,ethyl-benzene, m-xylene with p-xylene, o-xylene, 1,2,4-Trimethylbenzene,1,3,5-Trimethylbenzene, and 1,2,4,5-Tetramethylbenzene.

Example 4

As depicted in FIG. 12B, a chromatogram and a focused section of achromatogram are shown, depicting the results of a twenty minute trapand desorption of an indoor air sample, collected using only the deviceitself as described in FIG. 12A. The peaks shown are all volatileorganic compounds present in the room at trace concentrations (e.g. ppbor ppt). The graph and its subplot are zoomed in on a portion of thechromatogram to demonstrate the quantity of resolved peaks, theabundance of narrow peaks, excellent peak shape, and resolution betweenpeaks.

The disclosures of each and every patent, patent application, andpublication cited herein are hereby incorporated herein by reference intheir entirety. While this invention has been disclosed with referenceto specific embodiments, it is apparent that other embodiments andvariations of this invention may be devised by others skilled in the artwithout departing from the true spirit and scope of the invention. Theappended claims are intended to be construed to include all suchembodiments and equivalent variations.

1. A system for analyzing a gas mixture, comprising: a filter; a trap; achromatographic column; a detector; and a pump, wherein the trap and thepump are fluidly connected to form a first gas flow path, and whereinthe filter, the trap, the chromatographic column, the detector, and thepump, are fluidly connected to form a second gas flow path.
 2. Thesystem of claim 1, wherein the detector and the pump are fluidlyconnected to form a third gas flow path.
 3. The system of claim 1,wherein the chromatographic column is selected from the group consistingof a gas-solid adsorption chromatographic column, and a gas-liquid gaschromatography column.
 4. The system of claim 1, wherein the trapfurther comprises an adsorbent material.
 5. The system of claim 1,wherein the filter is an activated charcoal filter.
 6. The system ofclaim 1, wherein the detector is selected from the group consisting of aphoto ionization detector, a mass spectrometer, a spectrophotometer, anda thermal conductivity detector.
 7. The system of claim 1, wherein thedetector is a photo ionization detector.
 8. The system of claim 1,wherein the pump provides negative pressure.
 9. The system of claim 1,further comprising a housing.
 10. The system of claim 9, wherein thehousing is no larger than 216 cubic inch.
 11. The system of claim 1,wherein the system is capable of detecting chemical compounds with asensitivity of parts-per-trillion.
 12. A method of analyzing at leastone chemical compound in a gas mix, the method comprising: directingflow of the gas mix through a trap to concentrate at least a quantity ofthe chemical compound; redirecting flow of the gas mix through a filterto provide a filtered gas flow to the trap; releasing at least aquantity of the concentrated chemical compound into the filtered gasflow; and analyzing at least a quantity of the released concentratedchemical compound; wherein the direction of flow of the gas mix throughthe trap is opposite the direction of flow of filtered gas through thetrap.
 13. The method of claim 12, wherein the at least one chemicalcompound comprises at least one organic compound.
 14. The method ofclaim 13, wherein the at least one organic compound comprises at leastone volatile organic compound.
 15. The method of claim 12, whereinanalysis of at least a quantity of the released concentrated chemicalcompound comprises running at least a quantity of the releasedconcentrated chemical compound through a gas chromatography column. 16.The method of claim 15, wherein the gas chromatography column isselected from the group consisting of a gas-solid adsorptionchromatographic column, and a gas-liquid gas chromatography column. 17.The method of claim 12, wherein analysis of at least a quantity of thereleased concentrated chemical compound comprises identifying theorganic compound by a method selected from the group consisting of photoionization, mass spectrometry, spectrophotometry, and thermalconductivity.
 18. The method of claim 17, further comprising quantifyingthe chemical compound.
 19. The method of claim 12, wherein the gas mixis an environmental gas mix.
 20. The method of claim 12, wherein the gasmix comprises gases exhaled or otherwise originating from a humansubject.
 21. The method of claim 12, wherein the gas mix is air.